L5: The Nervous System: General Organization and Histology Flashcards
What makes up the CNS
The brain and spinal cord
What makes up the PNS?
The cranial and spinal nerves
What are the two subdivisions of the PNS?
Sensory (afferent) division
Motor (efferent) division
What does the sensory (afferent) division do?
- Convey impulses to the CNS
- All sensory information coming in
What does the motor (efferent) division do?
- Takes info from the CNS to the motor/effector organs
What are the two divisions of the motor/efferent division?
Somatic nervous system
Autonomic nervous system (ANS)
What does the somatic nervous system do?
- The “voluntary” nervous system
- Conducts impulses from the CNS to skeletal muscles
What does the autonomic nervous system do?
- the “involuntary” nervous system
- Regulates motor fibres in smooth muscles, cardiac muscles, glands
Has two subdivisions
What part(s) of a neuron are considered cytoplasmic processes
Dendrites
Axons
What is the function of a dendrite
- To convey incoming messages to the cell body
What is the function of an axon
- To generate a nerve impulse and transmits info/the impulse away from the cell body
What is a cluster of neuronal cell bodies in the CNS called?
nucleus
What is a cluster of neuronal cell bodies in the PNS called
Ganglia
What is a nissl body/ nissl substance?
- Clusters of rough ER on a neuron’s cell body
What is an axon hillock?
The cone shaped region where the axon extends off from the cell body
What are unipolar neurons?
- Has a single cytoplasmic process
- True unipolar neurons are only found in invertebrates
- We have pseudounipolar neurons
- Cell bodies are found in ganglia within PNS
- Ex. Sensory neurons
What are bipolar neurons?
- Has two cytoplasmic processes
- Found in special sense organs (eye/ear)
What are multipolar neurons?
- Have 3+ cytoplasmic processes
- Most common type of neuron in CNS
What do sensory “afferent” neurons do and what are their structure?
They carry info towards the CNS
They are pseudo-uni polar with cell bodies located in ganglia of PNS
What do motor “efferent” neurons do and what are their structure?
They carry info away from the CNS
Multipolar with cell bodies in CNS
What do association/interneurons do and what are their structure
- Located between sensory and motor neurons
- Multipolar and found within CNS
What are astrocytes?
- Small star shaped glial cells with many cytoplasmic extensions
- Most abundant supporting cell
- Functions in maintaining the integrity of neural tissue
What are microglia?
- Small oval shaped supporting cells with cellular processes
- Accounts for small portion of glial cells in CNS
- Monitors health and welfare of the neurons
- Originate from white blood cells and “clean up garbage” like microphages in CT
What are ependymal cells
- Cuboidal shaped glial cells
- Have cilia
- Line cavities found in brain and spinal cord
- Play important role in production and circulation of cerebral spinal fluid
What are ogliodendrocytes?
Glial cells that wrap around nerve fibers in CNS
- Make up myelin sheaths
- Relatively large
- Looks like an octopus
- Has lots of “tentacles” that can wrap around a short segment of 60 axons
What are the two supporting cells in the PNS
1) Schwann cells
2) Satellite cells
What do Schwann cells do?
- Surround and form myelin sheath around nerve fibres in PNS
What do Satellite cells do?
- Surround neuronal cell bodies with ganglia
- Plays a role in controlling the chemical environment of the neuron
- Modified Shwann cells
